Slice2Java code generation

Please can you consider these improvements for the slice2java codegen:
1. For structs and classes with data properties, generated classes implement java.io.Serialization. This makes it possible to use these classes/object instances with other java components (e.g. distributed caches such as ehcache/coherence).
2. For structs and classes with data properties, provide implementations of the hashcode() and equals() methods. This makes the classes directly usable in hashsets, for example.